Antigen-containing sustained release devices, such as polymer-based devices and liposomes, can be administered to effectively stimulate an immune response. The devices, however, must be of a size sufficient to permit an antigen presenting cell, such as a macrophage, to engulf and then process the antigen for presentation to T lymphocytes. See, for example, U.S. Pat. Nos. 5,942,252, 6,024,983, 5,811,128, 5,814,344, and 5,853,763 to Tice et al., U.S. Pat. No. 6,015,576 to See et al. and Tabata, Y. and Ikada, Y., “Phagocytosis of Polymer Microspheres by Macrophages” Adv. Polym. Sci. 1990, 94, 110–141, the entire contents of which are hereby incorporated by reference. Another method of delivery in which the size of the delivery device is critical, is the systemic delivery of efficacious levels of drugs by absorption of drug-containing delivery devices in the Peyer's patches of the gastrointestinal tract. This need for small delivery devices, presents difficulties and disadvantages in both processing and handling of these devices. Therefore, a need exists for improved methods and compositions for targeted delivery of biologically active agents where a small delivery device is needed to obtain delivery of sufficient levels of the agent.